title: Correlation between extraocular muscle size and motility restriction in thyroid eye disease.
abstract: OBJECTIVE
  Evaluate the relationship between extraocular muscle (EOM) size, measured by computed tomography, and ocular motility in thyroid eye disease (TED).
  
  
  METHODS
  This case series is based on a retrospective review of the records of 54 patients (108 orbits) with TED. Main outcome measures included EOM size and degree of motility restriction. The average diameter of each rectus muscle was compared with published norms. Four subpopulations based on Age (< 40 or ≥ 40 years) and State of thyroid eye disease (active or stable) were studied. Versions were measured by the corneal light reflex method. The trend of muscle diameter versus motility restriction was evaluated.
  
  
  RESULTS
  The average EOM diameter was greater than the norm in the study cohort and 4 subpopulations. The average diameter was largest in the Older and Active TED subpopulations. The inferior rectus and medial rectus were most frequently restricted in the study cohort and 4 subpopulations. The medial rectus had the strongest trend between increasing diameter and motility restriction, followed by the inferior rectus and the superior muscle group (comprised of the superior rectus and levator palpebrae superioris). However, there was a general lack of strong correlation between the diameter of the rectus muscles and their respective motility, especially in the Younger subpopulation.
  
  
  CONCLUSIONS
  EOM diameters are larger and have more restricted motility in the Older and Active TED subpopulations. Contrary to prior publications, the correlation between EOM diameters and motility was weak, especially in the Younger subpopulation. These findings suggest that the pathophysiology of EOM enlargement is different based upon the age of the patient and the activity of the orbitopathy.
authors.affiliation: Division of Ophthalmic Plastic and Reconstructive Surgery, Department of Ophthalmology, Edward S. Harkness Eye Institute, Columbia College of Physicians and Surgeons, New York, New York, USA.
authors.forename: Lora R
authors.initials: LR
authors.lastname: Dagi
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Zoumalan
authors.forename: Hindola
authors.initials: H
authors.lastname: Konrad
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Trokel
authors.forename: Michael
authors.initials: M
authors.lastname: Kazim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001767:Blinking; D005260:Female; D049970:Graves Ophthalmopathy / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015835:Ocular Motility Disorders / Q000000981:diagnostic imaging / Q000503:physiopathology*; D009801:Oculomotor Muscles / Q000000981:diagnostic imaging / Q000473:pathology*; D009929:Organ Size; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed